1. Field of the Invention
The present invention relates to a mobile communication system and a method therefor, and in particular to a method and an apparatus for estimating the location of a mobile station.
2. Description of the Prior Art
With recent development of mobile communication technique, there have been inexpensively provided mobile terminals, such as a portable telephone, a PHS (Personal Handy Set), and a pager. This provision varies services employing the mobile terminals.
Among the services is a service that estimates the location of a mobile apparatus or a person carrying a mobile apparatus. The service specifies the location, for example, by pursuing or chasing the radio wave radiated from the mobile apparatus, e.g., a radio apparatus. The service is-available to a building management system, which manages the location and the entrance and exit of a person carrying an ID card capable of communicating, through transmitting and receiving radio waves and infrared rays to/from the ID card.
Assuming such a location estimating service is provided using a PHS, the location of a person carrying the PHS is specified by clarifying which of cells the person exists in. The specifying is accompanied by an error because the cells have a given extent or expanse. Since the error depends upon the radius of the cells, even the smallest cell might cause an error, i.e., several hundred meter equivalent to the radius of the cell. On the other hand, assuming the location estimating service is provided using a portable telephone, the location of a person carrying the portable telephone is specified with a larger error because the cells used therefor are larger in radius than those used for the PHS. To summarize, the conventional mobile communication system involving a PHS and a portable telephone for the location estimating service has failed to accurately estimate the location of a mobile station.
It is therefore an object of the present invention to provide a mobile communication system and a method therefor capable of accurately estimating the location of the mobile station.
According to one aspect of the present invention, a plurality of base stations transmit and receive a frame to/from the mobile station. A manage station unifies the plurality of base stations. The manage station comprises an estimating circuit which estimates the location of the mobile station based upon a plurality of locations of the plurality of base stations and a plurality of distances between the plurality of base stations and the mobile station.
According to another aspect of the present invention, there is provided a manage station for use in a mobile communication system including a mobile station and a plurality of base stations communicating with the mobile station. The manage station comprises an estimating circuit which estimates the location of the mobile station based upon a plurality of locations of the plurality of base stations and a plurality of distances between the plurality of base stations and the mobile station.
According to still another aspect. of the present invention, there is provided a method of estimating the location of a mobile station in a mobile communication system in which the mobile station and a plurality of base stations communicating with each other. The method comprises the steps of measuring a plurality of distances between the plurality of base stations and the mobile station; preparing a plurality of circles each representing one of the locations of the plurality of base stations and the corresponding one of the plurality of distances to acquire a point at which the plurality of circles cross; and estimating the location of the mobile station based upon the point.